1. Field of the Invention
The present invention relates to a method for the assembly of automotive vehicles.
2. Description of the Related Art
Generally, the method of the assembly of automotive vehicles basically comprises four steps, that is, a press molding step for forming vehicle body structuring members, such as bonnets, trunk lids and so on, an assembly step for mounting these vehicle body structuring members to vehicle body sections into a white vehicle body section, a coating step for coating the white vehicle body section with coating paints, and a vehicle body assembly step.
The white vehicle body section assembly step further comprises an aligning step for aligning an assembly of each of a floor panel, a front body section and a rear body section with a pallet disposed in a vehicle body assembly line, an under vehicle body section assembly step for the assembly of the vehicle body sections by temporarily and additionally welding them, thereby forming an under vehicle body section, an aligning step for aligning the under vehicle body section with the vehicle body structuring members, such as the assembled body side panels, roof panels and so on, with the aid of exclusive aligning jigs by fixing the vehicle body structuring members on the basis of a reference surface of the outer panel, and a welding step for temporarily and additionally welding the resulting vehicle body section. The resulting vehicle body shell (white vehicle body section) is then conveyed to the coating step.
In the coating step, the vehicle body shell, or the white vehicle body section, is then subjected to chemical conversion treatment and further coated with under coating, intermediate coating and overcoating, as needed. Further, an anti-chipping paint may be coated prior to the intermediate coating or subsequent to the overcoating, as disclosed in Japanese Patent Laid-open Publication (kokai) Nos. 61-163,297 and 61-4,562.
When the vehicle body shell is coated in such a state that the lid members, such as the bonnet and the side doors, are temporarily mounted to the vehicle body shell, the lid members are generally removed from the vehicle body shell after the necessary coating has been finished, followed by mounting necessary parts, units, mountings or accessories to the lid members in an exclusive mounting line.
In the vehicle body assembly line, the parts, units, mountings or accessories, such as screws, grommets, fasteners, harnesses, trims, floor mats, instrument panel, seats and seat belts, are mounted to the vehicle body shell. Further, the lower part unit, such as the internal combustion engine, suspensions, tires and a fuel tank, are mounted. In addition, the lid members such as the bonnet and the side doors are mounted.
Japanese Patent Laid-open Publication (kokai) No. 64-1,667 discloses a holding apparatus for the assembly of the vehicle body shell in order to simplify the assembly operations of the vehicle body shells in the white vehicle body assembly step. This holding apparatus is so arranged as to perform the step for inserting a frame into the partially assembled vehicle body shell (at least prior to the mounting of the roof panel) through a roof opening section thereof and the step for assembling the rest of the vehicle body structuring members with the aid of plural clamping units or devices and tools mounted to the frame.
Recently, it has been proposed that the vehicle body shell should be separated into an upper vehicle body section and an under vehicle body section composed mainly of a floor panel. The upper vehicle body section and the under vehicle body section are separately assembled with the corresponding parts, units, mountings or accessories and then conveyed to the vehicle body assembly step, in order to simplify the operations in the vehicle body assembly step to a great extent. This step can further improve the efficiency in the mounting operations for mounting the lower part units and the various parts, units, mountings or accessories.
Further, Japanese Patent Laid-open Publication (kokai) No. 63-265,779 discloses a process of assembly of automotive vehicles, which involves coating each of the vehicle body structuring members constituting the upper vehicle body section and the under vehicle body section as well as the lid members, assembling the upper vehicle body section and the under vehicle body section separately, mounting the lid members and the mountings, etc. to the upper vehicle body section assembly, mounting the lower part units to the under vehicle body section to form an under vehicle body section assembly, and then combining the upper vehicle body section assembly with the under vehicle body section assembly.
This process, however, suffers from economical disadvantages because it increases the coating lines, it makes the coating step complicated, and it increases the number of conveying units and apparatuses, because each of the vehicle body structuring members such as the upper vehicle body section and the under vehicle body section is separately coated in the coating step. Further, it is difficult to provide both of the upper vehicle body section and the under vehicle body section with uniform coatings.
In addition, a conventional white vehicle body assembly step is so arranged as to assemble the white vehicle body sections with each other by setting each of the vehicle body structuring members on the basis of the outer panel thereof. This step, however, suffers from disadvantages that accuracy in assembling the white vehicle body may be lowered and various jigs are required so as to agree with the assembly of different models and kinds of white vehicle body section. This is because first, the outer panel is low in rigidity; secondly, the curved outer panel has the property of being returned to its original shape due to elasticity; thirdly, the alignment is performed merely by receiving the panel surface when the white vehicle body is fixed on the basis of the outer panel so that accuracy in the alignment becomes low; and, fourth, the jigs are not of general purpose type. The low accuracy in the assembly of the white vehicle body may become a cause of lowering the efficiency of operations, which follow, and may become an obstacle for the automation of the mounting operations.